| Pyridinium chlorochromate | |
|---|---|
 | |
 |  |
| IUPAC name | Pyridinium chlorochromate |
| Other names | PCC |
| Identifiers | |
| CAS number | [26299-14-9] |
| Properties | |
| Molecular formula | C5H5NHClCrO3 |
| Molar mass | 215. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 56 g/mol |
| Appearance | orange crystalline powder |
| Melting point | 205 °C |
| Solubility in other solvents | soluble in dichloromethane, benzene, diethyl ether, sol acetone, acetonitrile, THF |
| Hazards | |
| MSDS | external MSDS sheet |
| NFPA 704 |  3 3 |
| R-phrases | 49-8-43-50/53 |
| S-phrases | 53-45-60-61 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Pyridinium chlorochromate is a reddish orange solid reagent used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Dichloromethane ( DCM) or methylene chloride is the Chemical compound with the formula CH2Cl2 Benzene, or benzol, is an organic Chemical compound and a known Carcinogen with the molecular formula C 6 H 6 Diethyl ether, also known as ether and ethoxyethane, is a clear colorless and highly Flammable liquid with a low Boiling point and a Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless mobile flammable Acetonitrile (ACN is the Chemical compound with formula CH3CN "THF" redirects here For other uses see THF (disambiguation. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance Symbolism The four divisions are typically color-coded with blue indicating level of Health Hazard, red indicating R-phrases (short for Risk Phrases) are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon An aldehyde is an organic compound containing a terminal Carbonyl group. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or Pyridinium chlorochromate, or PCC, will not fully oxidize the alcohol to the carboxylic acid as does the Jones reagent. Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H The Jones oxidation is a Chemical reaction described as the Chromic acid oxidation of primary and secondary Alcohols to Carboxylic acids A disadvantage to using PCC is its toxicity. PCC was developed by Elias James Corey and William Suggs in 1975. Elias James Corey (born July 12, 1928) is an American organic chemist. Year 1975 ( MCMLXXV) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. [1]
Pyridinium dichromate is a similar oxidizing agent, which has the advantage of being less acidic. The Cornforth reagent ( pyridinium dichromate; PDC) is the complex of Chromium(VI oxide with aqueous Pyridine, with the chemical formula (C5H5NH2Cr2O7 An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound
Contents |
Preparation
The original preparation by Corey[1] involves adding one equivalent of pyridine to a solution of one equivalent of chromium(VI) trioxide and concentrated hydrochloric acid:
- C5H5N + HCl + CrO3 → [C5H5NH][CrO3Cl]
Agarwal et al. Pyridine is a Chemical compound with the formula C5[[Hydrogen H5]] N. Chromic acid generally refers to a collection of compounds generated by the acidification of solutions containing Chromate and Dichromate anions or the Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water presented an alternative synthesis that avoids the harmful side product chromyl chloride (CrO2Cl2). Chromyl chloride is a chemical compound with the formula CrO2Cl2 [2] Chromium(VI) oxide is treated with pyridinium chloride:
- [C5H5NH+]Cl− + CrO3 → [C5H5NH][CrO3Cl]
Properties and uses
PCC is primarily used as an oxidant. Pyridine is a Chemical compound with the formula C5[[Hydrogen H5]] N. An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound In particular, it has proven to be highly effective in oxidizing primary and secondary alcohols to aldehydes and ketones, respectively. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon An aldehyde is an organic compound containing a terminal Carbonyl group. A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or Rarely does over-oxidation occur (whether intentionally or accidentally) to form carboxylic acids. Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H A typical PCC oxidation involves addition of the alcohol to a suspension of PCC in dichloromethane. Dichloromethane ( DCM) or methylene chloride is the Chemical compound with the formula CH2Cl2 [3][4][5] A sample reaction would be:
- C5H5NHCrO3Cl + R2CHOH → C5H5NHCl + H2CrO3 + R2C=O
In practice the chromium byproduct deposits with pyridine as a sticky black tar, which can complicate matters. Addition of an inert adsorbent such as crushed molecular sieves or silica gel allows the sticky byproduct to adsorb to the surface, and makes workup easier.
PCC is also remarkable for its high selectivity. For example, when oxidizing tertiary allyl alcohols, unsaturated aldehydes are observed as the sole product. An allyl group is an Alkene Hydrocarbon group with the formula H2C=CH-CH2- An aldehyde is an organic compound containing a terminal Carbonyl group. This reaction is known as the Babler oxidation. Otherwise such oxidations commonly afford dienes as by-products resulting from dehydration.
Another notable oxidative reaction of PCC is its efficient conversion of unsaturated alcohols or aldehydes to cyclohexenones. Cyclohexenone is an Organic compound which is a versatile intermediate used in the synthesis of a variety of chemical products such as pharmaceuticals and fragrances This particular pathway is known as oxidative cationic cyclization. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge
Controversy
PCC is controversial as it contains chromium(VI). Hexavalent chromium ( Cr(VI) compounds are those which contain the element Chromium in the +6 Oxidation state. More environmentally friendly oxidants listed above are therefore favored by green chemists. An oxidizing agent or oxidising agent (also called an oxidant, oxidizer or oxidiser) can be defined as either a Chemical compound Green chemistry, also called sustainable chemistry is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous Other methods for oxidizing alcohols using less toxic reagents have been introduced:
- DMSO-based oxidations (Swern oxidation, Moffatt oxidation)
- hypervalent iodine based oxidation (such as the Dess-Martin periodinane)
References
- ^ a b Corey, E. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Dimethyl sulfoxide (DMSO is the Chemical compound with the formula (CH32SO The Swern oxidation, named after Daniel Swern, is a Chemical reaction whereby a primary or secondary Alcohol is oxidized to an Aldehyde The Pfitzner-Moffatt oxidation, sometimes referred to as simply the Moffatt oxidation, is a Chemical reaction which describes the oxidation of primary and Dess-Martin periodinane is a Chemical reagent used to oxidize primary Alcohols to Aldehydes and secondary Alcohols to Ketones J. ; Suggs, W. (1975). "Pyridinium Chlorochromate. An Efficient Reagent for Oxidation of Primary and Secondary Alcohols to Carbonyl Compounds". Tetrahedron Lett. 16: 2647-2650. Tetrahedron Letters is a weekly international journal for rapid publication of full original research papers in the field of Organic chemistry. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Agarwal, S; Tiwari, H. P. ; Sharma, J. P. (1990). "Pyridinium Chlorochromate: an Improved Method for its Synthesis and use of Anhydrous acetic acid as catalyst for oxidation reactions". Tetrahedron 46: 4417-4420. Tetrahedron is an international journal publishing full original research papers in the field of Organic chemistry. doi:. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
- ^ Paquette, L. A. ; Earle, M. J. ; Smith, G. F. (1998). "(4R)-(+)-tert-Butyldimethylsiloxy-2-cyclopenten-1-one". Org. Synth.; Coll. Organic Syntheses is a Scientific journal that since 1921 has provided the Chemistry community with annual collections of detailed and checked procedures Vol. 9: 132.
- ^ Tu, Y. ; Frohn, M. ; Wang, Z. -X. ; Shi, Y. (2003). "Synthesis of 1,2:4,5-Di-‘’O’’-Isopropylidene-D-erythro-2,3-hexodiulo-2,6-pyranose. A highly Enantioselective Ketone Catalyst for Epoxidation". Org. Synth. 80: 1. Organic Syntheses is a Scientific journal that since 1921 has provided the Chemistry community with annual collections of detailed and checked procedures
- ^ White, J. D. ; Grether, U. M. ; Lee, C. -S. (2005). "(R)-(+)-3,4-Dimethylcyclohex-2-en-1-one". Org. Synth. 82: 108. Organic Syntheses is a Scientific journal that since 1921 has provided the Chemistry community with annual collections of detailed and checked procedures
Further reading
- G. Tojo and M. Fernâandez (2006). Oxidation of alcohols to aldehydes and ketones : a guide to current common practice. Springer. ISBN 0387236074.
External links
- IARC Monograph "Chromium and Chromium compounds"
- History of PCC
- Datasheet PDC
- National Pollutant Inventory - Chromium VI and compounds fact sheet
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic